1. Field of the Invention
The present invention generally relates to a machine and method for loading nuclear fuel pellets into a nuclear fuel rod for use in a nuclear reactor.
2. Description of the Prior Art
Nuclear fuel pellets are classified as fuel, burnable poison (BP) or axial power shaping rod (APSR) pellets. Fuel pellets are used in nuclear fuel rods used to power the reactor. BP pellets are used in guide tubes of the fuel which tubes control the fuel reaction of the reactor. ASPR pellets are used in the axial power shaping rods of the reactor. Pellets are shaped in cylindrical form approximately xe2x85x9c inch in diameter and approximately xc2xd inch to xc2xe inch in length.
BP and APSR pellets are shipped to the fuel loading area in bulk since there is no criticality factor to consider as is the case in fuel pellets which may go critical if stacked more than 4 inches in height depending on the array. Therefore, fuel pellets are shipped to the fuel loading area in single layer corrugated trays approximately 8 inches square. This size tray is sufficient to fill a single 12-foot fuel rod.
The fuel rod loading process begins with the trays being visually inspected and any missing pellets being added to the trays. Since the enriched uranium in a fuel rod can be detected on a weight basis, the full trays are weighed to determine the desired enrichment for a single fuel rod and some of the pellets are then removed if necessary. The calibrated tray is then placed in a loading machine which aligns the first row of the tray with the open end of a 12-foot fuel rod. The rows of the tray are then sequentially pushed into the fuel rod until the entire tray is emptied into the fuel rod. This process is then repeated for the next fuel rod.
For bulk delivered nuclear pellets such as BP and APSR pellets it is known to load them into trays using rotating hoppers. Examples of such hopper loading systems are found in US Pat. No. 4,765,453 and U.S. Pat. No. 5,489,184. However, none of these patents teach an automatically operating machine where the pellets are automatically counted as they are placed on a tray to assure the proper number of pellets on the tray to fill a single fuel rod nor of automatically weighting the filled tray to insure the proper enriched uranium content of the fuel rod prior to automatically loading the pellets into the fuel rod.
To accomplish this a new machine was needed to automate these, previously manual processes.
The present invention solves the problems associated with prior art nuclear pellet loading machines and methods, as well as other, by providing an nuclear pellet loading machine which loads pellets into a nuclear tube.
The loading machine has a hopper which delivers the pellets loaded therein unto a conveyor belt which delivers them to a set of pinch rollers and unto a queuing tray comprising a series of 13 parallel rows for holding the pellets in the rows. The pinch rollers have a counting mechanism for counting the number of pellets being entered onto the queuing tray and controls the movement of the tray rows with respect to the pinch rollers to make sure each row has the proper number of pellets and that the tray has the proper total number of pellets. Once this tray is completed, its contents are moved unto an adjoining identical tray which has a weight apparatus associated therewith to weight the total pellets on the tray to conform the pellets to the needed reactivity of the nuclear tube to be filled. Once the proper weight is determined to be had, the contents of the tray are moved to a third identical loading tray from which the pellet contents are moved to have each row of the tray sequentially inserted in a straight line to a nuclear tube connected to the machine. Once each tray is emptied it returns to its home position and its process is repeated. Once the tube is filled and removed from the machine a new nuclear tube is aligned with the machine and the process of loading is repeated.
In view of the foregoing it will be seen that one aspect of the present invention is to provide a fully automated nuclear pellet-loading machine.
Another aspect of the present invention is to provide a fully automated nuclear fuel pellet-loading machine which provides fuel rods of desired enriched uranium content.
Yet another aspect of the present invention is to provide a fully automated nuclear pellet-loading machine able to load bulk pellets to reactor rods.
These and other aspects of the present invention will be more fully understood after a detailed review of the foregoing description of the preferred embodiment when considered with the accompanying drawings.